(CNN) -- Defending champion Venus Williams avenged a blot on her 2009 season to set up a last-16 clash with Ana Ivanovic at Wimbledon, but their fellow former world No. 1 Jelena Jankovic and French Open winner Svetlana Kuznetsova crashed out of the tournament on Saturday.

American Venus Williams is seeking to win her sixth Wimbledon singles title.

Williams crushed Carla Suarez Navarro 6-0 6-4 to obliterate memories of her upset defeat by the 34th-ranked Spaniard in the second round of the Australian Open in January.

The American stretched her winning run on grass at SW19 to 17 matches after winning the first eight games.

"In Australia I had a lot of opportunities but didn't take advantage of them," Williams told reporters.

"Today I realized that it wasn't the same match and I was determined to really run away with it. I knew what I did in that match. Obviously at this point I knew her game, too. In the end it got closer but I love to have the opportunity to serve matches out, so I was pretty glad for that break."

She next plays Ivanovic, with the Serbian 13th seed having earlier beaten 18th-seeded Australian Samantha Stosur 7-5 6-2.

Last year Ivanovic arrived at SW19 as the French Open champion and at the top of the rankings, but was stunned in the third round by Chinese wildcard entry Zheng Jie and then failed to win successive matches in her next five tournaments.

"At the moment I feel better on the court than I felt then," she said. "I feel my game has improved and my serve has improved. I get much more speed on it and much more variety.

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"I went through a lot over the past year, being number one, having some disappointing losses and some tough times. I think that made me stronger and made me appreciate some things, not take every match you win for granted, but just appreciate the hard work that was put in."

Ivanovic's sixth-seeded compatriot Jankovic, who last year topped the women's rankings despite never having won a Grand Slam tournament, was upset by American qualifier Melanie Oudin.

The 17-year-old Oudin, making her debut at the event, won 6-7 (8-10) 7-5 6-2 to earn a last-16 clash with Polish 11th seed Agnieszka Radwanska, who won 6-4 7-5 against 19th seed Li Na of China.

"My goal has always been, since I was little, to become number one in the world one day," Oudin said. "But I know that it's going to take a lot more work and I'm going to have to get better and better. But I'm willing to work on it."

Jankovic, who needed to call the physio after feeling dizzy in the first set, was less than generous in hailing her opponent, who had 38 winners to the losers 13.

"From what I have seen, she can play if you let her play," Jankovic said. "But she cannot hurt you with anything. She doesn't have any weapons, from what I've seen."

On the day of her 24th birthday, Russian fifth seed Kuznetsova was also dumped out by an unseeded teenager, losing 6-2 7-5 to 19-year-old German Sabine Lisicki.

World No. 41 Lisicki, who has reached the fourth round of a Grand Slam for the first time, will next face ninth seed Caroline Wozniacki.

"I'm just so happy," said Lisicki, who needed five match-points before sealing the biggest win of her career to date. "I just kept fighting. It was tough but I'm so happy to have pulled it out.

"It's a huge win for me because before Wimbledon I had not won a match on grass, so I can't believe I'm in the fourth round. My parents and best friend were here today, so it's the best thing that could have happened."